Many people don’t see why they should write down their thoughts and ideas. They think (that’s what they say) that they’ll remember the good ones anyway.
I always advise friends to write down whatever comes into their heads (well, not everything, of course).
First, because you do forget. Even good ideas are very easy to forget, lose or let slip if something suddenly distracts you.
Second, a thought written on paper no longer looks so brilliant as it did when it was only in your head.
Recently I came up with what I think is a good comparison to illustrate this:
(it only works for people with a bad ear for music, like me)
Think of some very well-known tune. Try playing it in your head. Come on, something famous. Anything at all… Got it?
Right, now try to reproduce it out loud!
Hum it, or drum it out with your fingers… Worse now, isn’t it?
For me it’s a lot worse…
Same with ideas. Even when you do write one down in your notebook: super! great! how clever of me to think of that!
And you go to bed.
Next morning you reread it: well, not such a brilliant idea after all. You google it: damn, there’s plenty of this already… Need something different.